64 PRACTICAL ORGANIC CHEMISTRY over small pieces of calcium chloride. It is decanted or filtered from the calcium chloride and distilled. The distillate is collected at 130 — 132°. The yield is nearly equal to the weight of bromine taken. Properties. — Colourless liquid, which solidifies, at o° to a crystalline mass and melts at 9° ; b.p. 131'S0 ; sp.gr. 2*19 at if. Reaction.— Attach a 100 c.c. flask to a short upright con- denser (see Fig. 86) and to the upper end of the condenser attach a vertical delivery tube, dipping into an ammoniacal cuprous chloride1 solution. Pour i — 3 c.c. of ethylene bromide into the flask with 4 times its volume of strong methyl alcoholic potash, which is prepared by boiling methyl alcohol with excess of caustic potash on the water-bath with upright condenser. On gently heating, a rapid evolution of acetylene occurs and the characteristic brown copper compound (C2H2Cua,H2O) is pre- cipitated from the cuprous chloride solution. Acetyene. See Appendix, p. 237. PREPARATION 5. Acetaldehyde, CH3.CO.H Liebig, Annalen^ 1835, 14, 133 ; Staedeler, /. prakt. Cheni., 1859, (076, 54- 100 grms. potassium bichromate 420 c.c. water. A mixture of 100 grms. (125 c.c.) absolute alcohol and 140 grms. (75 c.c.) cone, sulphuric acid. 100 c.c. methylated ether, which has been left to stand over solid caustic potash for a few hours, and then distilled off from the water-bath. A round flask (i-| litre) is provided with a double-bored cork. washed once or twice by decantation and dissolved in a strong solution of ammonium chloride. When required a little ammonia is added sufficient to give a clear blue solution.